Abstract
Isolated lymph node cells incorporate inorganic orthophosphate into a protein fraction. The phosphorylated product is a phosphoprotein. The rate of phosphate incorporation into phosphoprotein was determined in cells isolated from regional lymph nodes at varying times after antigen injection. The rate was unaltered on the 3rd day, but was enhanced on the 4th day after injection. Parallel results were obtained with L-methionine incorporation into the same gross protein fraction. Possible relationships between antibody formation and the observed enhancement in phosphate incorporation into phosphoprotein are discussed.